1. Field of the Invention
The present invention relates to a paper sheet receiving/dispensing apparatus, and more particularly, to a paper sheet receiving/dispensing apparatus, provided with strip films for receiving or dispensing a paper sheet, for controlling a running velocity of the strip films to be stably constant with high precision.
2. Description of the Related Art
Conventionally, there are bill receiving/dispensing apparatuses of a bill recycling unit (hereinafter abbreviated to BRU) that is included, for example, in an ATM (Automated Telling Machine) or the like used in a financial institution or the like. Also a ticketing machine installed in a station yard or the like includes a paper sheet receiving/dispensing apparatus.
Such units include a paper sheet receiving/dispensing apparatus of a strip film type for receiving and dispensing a bill or a ticket (hereinafter referred to as a paper sheet).
This paper sheet receiving/dispensing apparatus is sometimes used as an apparatus dedicated to receipt and dispensing of a paper sheet, dedicated to receipt of a paper sheet, or dedicated to dispensing of a paper sheet.
Structures of such apparatuses dedicated to receipt and dispensing of a paper sheet, dedicated to receipt of a paper sheet, and dedicated to dispensing of a paper sheet are almost identical. Therefore, these apparatus are described below uniformly as a paper sheet receiving/dispensing apparatus.
This paper sheet receiving/dispensing apparatus has advantages that paper sheets can be received and dispensed at low cost without providing a complicated mechanism, many paper sheets can be wound and dispensed with a small capacity, and many types of bills can be received and dispensed only by additionally providing an individual paper sheet receiving/dispensing apparatus.
When receiving a paper sheet, this paper sheet receiving/dispensing apparatus sandwiches the paper sheet between two strip films, and receives the paper sheet by winding the sandwiched paper sheet around a winding drum along with the two strip films.
Additionally, when dispensing a paper sheet, the paper sheet receiving/dispensing apparatus dispenses the paper sheet by rewinding the two strip films wound around the winding drum along with the paper sheet.
Incidentally, in the structure of such a paper sheet receiving/dispensing apparatus, a drum diameter of the winding drum (not the diameter of the drum itself but an outer diameter of the strip films that sandwich a paper sheet and are wound. The same applies hereinafter) increases as the strip films and the paper sheet are being wound around the drum when receiving the paper sheet.
Inversely, when dispensing a paper sheet, the drum diameter decreases as the strip films and the paper sheet are being dispensed.
It is preferable to normally make the receiving velocity and the dispensing velocity of a paper sheet constant in paper sheet receiving/dispensing apparatuses without being limited to the strip film type.
If the receiving velocity or the dispensing velocity of a paper sheet increases or decreases, a velocity difference occurs in a passing part between the paper sheet receiving/dispensing apparatus and a paper sheet conveyance path of a parent machine provided with the paper sheet receiving/dispensing apparatus.
If the velocity difference occurs in the passing part as described above, a paper sheet is stretched or loosened by the passing part.
Such tension changes of a paper sheet in the passing part lead to a paper sheet jam. To prevent the paper sheet jam, the receiving velocity and the dispensing velocity of a paper sheet need to be kept constant.
In the meantime, if an angular velocity of a drum is made constant in the paper sheet receiving/dispensing apparatus of the strip film type, a surface linear velocity of a drum diameter, namely, the running velocity of strip films is fast when the drum diameter is large. Therefore, the receiving or dispensing velocity of a paper sheet becomes fast.
Inversely, if the drum diameter is small, the surface linear velocity, namely, the running velocity of the strip films is slow. Therefore, the receiving or dispensing velocity of a paper sheet becomes slow.
If the receiving velocity or the dispensing velocity of a paper sheet increases or decreases, a problem such as a paper sheet jam occurs in the passing part as described above.
To prevent this problem, it is necessary to control the surface linear velocity of a drum diameter to be constant regardless of whether the drum diameter is either large or small.
To control the surface linear velocity of the drum diameter to be constant, the drum diameter being operated needs to be detected.
For the detection of a drum diameter, for example, Japanese Laid-open Patent Publication No. HEI10-181972 proposes a tape velocity control device for calculating the running velocity of a tape (equivalent to the above described strip film) on a winding drum from an obtained drum diameter and the angular velocity of the winding drum after calculating the drum diameter from the number of rotations of the winding drum, or after calculating the drum diameter from the number of received paper bills.
For the above described detection of the number of rotations of the winding drum, an encoder sensor is provided on a shaft of a motor that drives the running of tapes and rotations of the winding drum via a timing belt, and the number of rotations of the motor is obtained from the number of pulses of a pulse signal output from the encoder sensor.
Then, the number of rotations of the winding drum is obtained from the number of rotations of the motor, and the drum diameter is calculated from the number of rotations of the winding drum, so that the running velocity of the tape on the winding drum is detected from the calculated drum diameter.
However, if the running velocity of the tape suddenly changes such as at the winding or dispensing start of the tape, a slide occurs between the tape and a pulley.
Also if impurities such as dust, paper dust or the like adhere to the timing belt or the pulley while the device is being operated, a slide similarly occurs between the timing belt and the pulley.
Additionally, a relative change occurs in a driving force between the tape and the pulley depending on an environmental condition such as a temperature, humidity or the like at an installation site of the device.
If the slide or the relative change of a driving force occurs between the tape and the pulley as described above, the pulse signal output from the encoder sensor becomes inaccurate.
If the number of rotations of the motor, the drum diameter and the running velocity of the tape are calculated based on the inaccurate pulse signal and the rotational velocity of the motor is controlled based on the calculations, a desired rotational velocity of the motor cannot be achieved.
If the desired rotational velocity of the motor cannot be achieved, the receiving velocity or the dispensing velocity of a paper sheet cannot be kept at a predetermined constant velocity.
In such a case, the problem such as a paper sheet jam or the like is caused by the stretch or the looseness of a paper sheet as described above.
Additionally, if the tape and the pulley are engaged more tightly in order to prevent the slide between the tape and the pulley, a frictional force or a load imposed on both of the members increases, leading to shortening of lifetime of the tape such as an early-stage cut of the tape due to its wear-out and the like as well as shortening of the lifetime of both of the members.